The present invention relates generally to elevators and, in particular, to an elevator door drive apparatus with a door locking mechanism.
A door drive device with a latching mechanism for use with elevators is shown in the European patent document EP-OS 0 164 581. The device includes an entraining member parallelogram which is arranged at the car door for the coupling of the car door with a shaft door through cooperation with two rollers fastened at each shaft door. A pawl, which is controlled by the entraining member parallelogram and an angle lever, on the one hand holds the car door in a latched setting with the entraining member parallelogram closed to permit the free passage of the car past a floor and, on the other hand, unlatches the car door with the fully opened entraining member parallelogram adjacent a floor, for example in the case of a power failure. The pawl is opened when the car is situated in the region of a floor by a control roller attached to an angle lever which roller runs up onto a control cam located at the shaft door and turns the angle lever which releases the pawl from the latching position. This unlatching takes place for every destination floor or, in the case of a power failure, when the elevator car is situated within the door opening zone of a floor. The car door and the coupled shaft door are, according to the state of the elevator control, either opened automatically by the door drive or can be pushed open manually. The car door, however, remains latched when the elevator car, for example in the case of a power failure, is situated outside the door opening zone of a floor.
A disadvantage of the above-described device is that a control cam is required at each shaft door on each floor for unlatching the car door. These control cams must cooperate exactly with the drive device located on the car and, therefore, require accurate and expensive installation procedures at the building site.
Another elevator door drive device with a latching mechanism with a similar mode of construction is shown in the European patent document EP-A-0 332 841. In this device, the car door is likewise connected with the shaft door by a coupling mechanism in the region of the floors, wherein again an entraining member parallelogram located at a car door leaf and two coupling rollers arranged at each shaft door leaf cooperate. The closed entraining member parallelogram passes between the coupling rollers of a shaft door during travel past a floor, but couples with the coupling rollers through the opening of the entraining member parallelogram at a destination or target floor. The closing of the entraining member parallelogram in the normal case is actuated through the door drive device. An actuating lever, which is connected with a belted drive means of the door drive device and the entraining member parallelogram and which is pivotable to and fro between two fixedly placed elastic abutments, closes the entraining member parallelogram through a pivotal movement in a counterclockwise direction. The opening of the entraining member parallelogram is performed by the application of force applied by a tension spring engaging the actuating lever and the base plate of the entraining member parallelogram, either in the case of a lack of power to the drive motor or in the case of reversing of the drive motor, which is regulated by a microprocessor, to the opening direction. If this opening takes place within the door opening zone of a floor, the entraining member parallelogram is held by the coupling rollers of the shaft door in a central position, wherein a ramp cam of the entraining member parallelogram is pressed together in a parallel direction and a control cam located at the ramp curve unlatches the car door latch. At the same time, the entraining member parallelogram is latched in this central position by an additional latching device.
Disadvantages of this device are that a laborious and expensive installation procedure is required for the door drive motor for an unobjectionable door actuation, that the entraining member parallelogram and the car door latching means are arranged spatially one beside the other and the door drive device is usable only conditionally when different height shaft doors must be actuated for the same elevator, and that an additional latching device is required for the open entraining member parallelogram for the opening movement of the doors by the door drive device.